I speak as someone who spent 30 years in Civil Service, then had to find a private sector employer. Here is my four pennyworth.
If you were to pay even £5000 for professional advice from someone who
does not get commission it would likely work out better than being sold a product on the basis of how much commission the advisor gets.
Split your investments across at least two completely separate providers in case of catastrophe, and study carefully the rules on compensation for failure. Here is a link to a starting point.
Compensation : FSA Money made clear ? about the FSA - on the assumption you are British.
The longer you have to go until retirement the greater the risk you can run, but even if you are in your twenties I would still suggest you should put some part of your investment into something really safe like Government Bonds. Look for funds with the lowest management fee, makes a huge difference over the decades. It may be worth putting as much as you can into an ISA, where the returns are tax free even after retirement. Compare with pension funds where you get your pension funds investment grossed up but you have to pay tax on your pension when you retire. Remember thanks to GB pension investments are not so favourably treated as they once were - some folk will word this more strongly!
Take a relaxed long term view over the value of your share portfolio but watch changes in charges made by your provider like a hawk. Some companies used to charge 0.25% pa on tracker funds and now charge 1% pa.
I am not a financial expert, don't take anything on trust from me, or any other single source.
I hope this helps.